Hey everyone, here's a first glimse of my restarted project, DarkMatter.
Check out the repo for the engine-side development on GitHub for more details and downloads: github.com/themuffinator/dm-engine

Still a lot of room for improvements but I think some folks might get some enjoyment out of it so far and potentially have some feedback to give. Check out the assets/docs/darkmatter-todo to get an idea of how I'm looking to develop the source port.
Edited 32 seconds after the original posting.

Very interesting. I will check it out and follow the development.
For my understanding, the goal is to create one engine for q1, q2 and q3 so easily switch between them. Like you start a dark matter server and you go from playing a q1 map to a q3 map without switching games?
Edited 28 seconds after the original posting.

Yeah you have the right idea. Maps from the different titles would apply the appropriate physics and game rules from the original game code. A lot of work to be done though, but luckily on the game logic side I have a lot of workable code from previous projects that can be ported over.

Given the major architectural changes between even just Q2 vs Q3, you're setting yourself up for pain... Quake3 started off as a clean slate around May 1997 as Trinity since johnc wanted to dump all the software rendering baggage and old methods with a prospect to leverage the new dawn of 3d hardware. Getting the old baggage back in (progs interpreter/ game module loading and their different conflicting builtins, old bsps with internal textures, animated lightmaps, leafs, etc) is going to be a very long and clunky journey.

If you want an existing example, there's FTEQW, which started as a quakeworld source port to add some modern things (as in loading TGAs, oggs, skyboxes), then support for other games were gradually creeped in ("netquake", Hexen II, Quake2, Quake3) with varyingly "off" results.
Edited 35.43 minutes after the original posting.

I think the results will be worth the effort.

Yeah FTE has some similar features to what we set out to do.